Research has indicated that brief motivational interventions (BMIs) may be efficacious in reducing at-risk drinking among college students (Larimer & Cronce, 2007). On the other hand, the literature has shown mixed findings regarding the efficacy of different types of BMIs for different groups of at-risk college drinkers. Further, theory and empirical research have provided preliminary evidence that BMIs may be more optimally matched to certain levels of motivation (Collins & Carey, 2005; Collins et al., 2005); however, motivational measures have not always been shown to be psychometrically sound in the college population. Considering these mixed findings, this study will clarify and build on the literature regarding the efficacy and underlying mechanisms of BMIs among at-risk college drinkers. First, it will test the efficacy of 2 web-based BMIs, decisional balance exercises (DBE) and personalized normative feedback (PNF), compared to assessment- only control (AO). It is hypothesized that PNF and DBE will be associated with greater reductions in alcohol use and alcohol-related problems over the 12-month follow-up. The current study will also test the decisional balance proportion (DBP), or the proportion of participant-generated pros of reducing drinking and cons of current drinking to the total decisional balance, to serve as an innovative measure of motivation to change. It is hypothesized that DBP change (post-baseline) and baseline DBP scores will serve as mediators and moderators of the BMI effects, respectively. The final aim is to pilot a schema that may be used for subsequent a priori client-treatment matching to optimally match college drinkers to BMIs on the basis of their baseline motivational level. Preliminary validation of this schema will be conducted using generalized growth mixture modeling and sequential processes to test whether baseline levels motivation are adequate to predict participants' longitudinal trajectories following a BMI. The long-term goal is to examine the DBP as a measure of motivation to change and an optimal treatment-matching variable for web-based BMIs for at- risk college drinkers. Future studies may refine this treatment-matching schema and eventually generalize it to fit the needs of diverse populations to increase the overall efficacy of BMIs for alcohol use. PUBLIC HEALTH RELEVANCE: This study aims to increase the efficacy of secondary prevention for at-risk college drinking. In developing and testing a new participant-generated measure of motivation to change, web-based interventions and treatment matching technology, this study will address the strategic plan of the NIAAA: it will use innovative research technology to enhance brief motivational interventions and will develop and test new ways to deliver stepped and motivationally appropriate interventions to adolescents and emerging adults.